The efficacy and toxicity of daily, oral cyclosporin A (CSA) in patients with active rheumatoid arthritis is being evaluated in a 6 month double-blind study of low dose (lmg/kg/day) versus high dose (10mg/kg/day) CSA. Toxicity is monitored weekly for the first 2 months and then every 2 weeks until 6 months. Disease activity is assessed on a bi-monthly basis. Patients who do not develop at least a 40% improvement in disease activity at 6 months are dropped from the study, while those with a 40% or greater response continue for an additional 6 months of drug therapy. The effects of CSA on various measures of T lymphocyte function in peripheral blood and within the synovium is studied in all patients.